Differential and method for assembling said differential

ABSTRACT

The invention concerns a differential comprising axle pinions ( 5 ) and pinion gears ( 6 ) and a body ( 1 ) wherein are mounted said pinions. Said body ( 1 ) has two parts ( 2, 3 ) provided with complementary guiding means ( 11, 22 ). One of said two parts includes at least two inner guides ( 17 ) for mounting slidably a rotatable slave assembly pin ( 9 ) of the pinion gears ( 6 ). When the differential is assembled, the relative position of said two parts ( 2, 3 ) is adjusted so as to adjust the axial play of at least the axle pinions ( 5 ) or the differential drag torque. Then the two parts are locked relative to each other.

The present invention relates to differentials of which the body, inside which are mounted the axle pinions and the pinion gears, is in two parts. More precisely, it relates to this body, to a differential comprising this body, as well as to a method for assembling this differential.

A known differential comprises two substantially symmetrical half-shells. The latter, once assembled by clamping one against the other, form the body of the differential and jointly define a housing containing in particular two axle pinions, two pinion gears and two pierced dish elements, each disposed between one of the axle pinions and the body of the differential. Due to the manufacturing tolerance of the parts constituting this differential, an adjustment of the play between its gears is provided during assembly thereof. To that end, a plurality of dish elements of different thicknesses are successively mounted until those which enable the desired adjustment to be obtained have been found. Apart from being tedious, this manner of proceeding is long and must be carried out manually.

Patent document JP-58 211053 describes a differential, in a cage of which are screwed a first and a second tubular element. The adjustment of the play inside this differential requires adjusting both the position of the first tubular element and that of the second tubular element.

The invention therefore has for its object to facilitate the adjustment of a play inside a differential and/or the drag torque of this differential.

Within its meaning to be understood here, the drag torque of a differential is the torque which must be exerted on one of its axle pinions to drive this axle pinion when, the other axle pinion being free to rotate, the body of the differential is immobilized. As will have been understood, the drag torque depends in particular on the plays inside the differential.

For the purpose of attaining the object set forth hereinabove, the invention relates to a differential body inside which are intended to be mounted two axle pinions and at least two pinion gears, each in mesh with the two axle pinions, this body comprising first and second parts intended to be assembled, these first and second parts comprising complementary guiding means adapted to guide them in relative approach and removal along the axis of rotation of the differential, characterized in that the first part comprises at least two inner guides for slidably mounting at least one pin for rotatable assembly of at least one of the pinion gears, each of these two guides joining two points offset from each other in a direction parallel to the axis of rotation of the differential.

The invention also has for its object a differential comprising at least:

-   -   two axle pinions,     -   two pinion gears, each in mesh with the two axle pinions, and     -   a body inside which are mounted the axle pinions and the pinion         gears, this body comprising assembled first and second parts,         characterized in that the body is as defined hereinabove, at         least one pin for rotatable assembly of the pinion gears being         mounted to slide, the relative position of said first and second         parts being adjusted so that the axle pinions have a         predetermined axial play or so that the differential has a         predetermined drag torque, said first and second parts being         locked in this adjusted relative position.

Moreover, the invention has for an object a method for assembling the differential as defined hereinabove, characterized in that it comprises at least the steps in which:

-   -   a) at least the axle pinions and the pinion gears are disposed         between the first and second parts;     -   b) the relative position of said first and second parts is         adjusted so as to adjust the axial play of at least one of the         axle pinions or the drag torque of the differential, and     -   c) the first and second parts are locked in the position         determined during step b.

The invention will be more readily understood on reading the following description, given solely by way of example and made with reference to the accompanying drawings, in which:

FIG. 1 is a view in axial section of a differential according to the invention.

FIG. 2 is an exploded view, in perspective, and represents the body, in two parts one and the other according to the invention, of the differential of FIG. 1, one of these two parts being provided with two dish elements constituent of the differential.

FIG. 3 is a view in axial section of one of these two constituent dish elements of the differential shown in FIG. 1, and

FIG. 4 shows the dish element of FIG. 3, this dish element being viewed by that of its two opposite faces which is intended to be turned outwardly.

FIG. 1 shows a differential which is according to the invention and comprises a body 1 in two parts, namely a cage 2 and an obturator 3. In this body 1, which defines an inner housing 4, there are mounted two axle pinions 5, two pinion gears 6, two anti-friction dish elements 7 disposed opposite each other, two sliding dish elements 8 likewise disposed opposite each other and an assembly pin 9 which is engaged in the sliding dish elements 8 and bears the pinion gears 6.

As may also be seen in FIG. 2, the cage 2 is substantially in the form of a solid of revolution which has axis A of rotation of the differential as axis of revolution. It essentially defines the inner housing 4 and comprises an opening 10 for access to this housing 4. This opening 10 is defined by an end portion 11 of the inner surface of the cage 2. This end portion 11, which has a circular section, is machined and forms guiding means. It comprises two adjacent portions of which one is disposed more deeply than the other and referenced 12, and of which the other is referenced 13. Portion 12 is tapped, while portion 13 is bored.

Beyond the inner housing 4, the cage 2 extends in a tubular portion 14 which is disposed and directed opposite the access opening 10, and which is provided for the passage of a transmission shaft (not shown) intended to be coupled to one of the axle pinions 5.

Between the end portion 11 and the tubular portion 14, the inner surface of the cage 2 comprises a substantially cylindrical portion 15 adjacent the end portion 11, then it terminates in a bottom surface 16, which, for its part, is concave and substantially spherical. At the level of the portion 15, it defines two inner grooves 17, disposed opposite and substantially axial. Each of these grooves 17, of which the respective bottoms and sides are planar, forms a guide in which is slidably mounted one of the two dish elements 8.

In the vicinity of its access opening 10, the cage 2 comprises an outer, radial ring 18 which forms a flange for fixing by clamping a crown wheel (not shown) provided for drive of the differential. The radial ring 18 is pierced with holes 19 for the passage of screws (likewise not shown), for fixing the crown wheel.

The cage 2 is a forged part in one piece. It is preferably made of a light alloy such as an aluminium alloy. Except for the end portion 11, its inner surface is not machined, this compensating, at least in part, the additional costs involved by the use of forging, compared to a method of moulding.

The obturator 3 is likewise substantially in the form of a solid of revolution of which the axis is the axis A of rotation of the differential. It comprises a tubular part 20 which is provided for the passage of another transmission shaft (not shown) intended to be coupled to one of the axle pinions 5. This tubular part 20 widens then extends in a thick, radial, annular cover 21.

The lateral edge of this cover 21 is defined by a cylindrical surface 22, which forms complementary guiding means of the end portion 11. Like the latter, the cylindrical surface 22 is machined and comprises a smooth portion 23 and a threaded portion 24.

The inner wall 25 of the lid 21 partly defines the inner housing 4. In its central part, it is also concave and substantially spherical.

The two sliding dish elements 8 are identical, this being translated, on the one hand, by a simplification of the assembly of the differential and, on the other hand, by a saving. One of them is shown in FIGS. 3 and 4 and is substantially annular in shape. It comprises a substantially tubular base 26, of which the inner section is circular and whose outer section is likewise circular except at the level of two rectilinear shoulders 27, parallel to each other and arranged opposite each other. The lateral faces 28 of these two shoulders 27 are intended to cooperate with the sides of the grooves 17, in order to ensure, on the one hand, guiding of the corresponding dish element 8, particularly during assembly thereof and, on the other hand, the transmission of the efforts between the cage 2 and the assembly pin 9.

The inner surface of the base 26 defines a housing for one of the ends of the assembly pin 9. In the example shown, this housing has a circular cross section so that it behaves like a bearing.

From the base 26 there widens a seat 29 for one of the pinion gears 6. The inner surface of this seat 29 is a surface of revolution which is concave and substantially spherical, and it is separated from the inner surface of the base 26 by an annular flange 30, directed along the axis of the dish element 8 and provided for centering one of the pinion gears 6.

Each dish element 8 is a part in one piece, cold-forged and made of a metal.

Each of the gears 5 and 6 is known per se and presents a conical toothing and a convex and substantially spherical outer face.

Each dish element 7 presents the shape of a plate of small thickness, pierced with a central hole for the passage of a transmission shaft and convex in the manner of a substantially spherical dome.

The assembly pin 9 is formed by a cylindrical bar of circular section.

In order to assemble the differential shown in FIG. 1, a dish element 7, then an axle pinion 5, are firstly introduced inside the cage 2.

Then, after having fitted the two pinion gears 6 and the two dish elements 8 on the assembly pin 9, the assembly thus formed is engaged in the housing 4, taking care to place the bases 26 of the elements 8 in the grooves 17. This assembly is then pushed towards the bottom of the cage 2, by simultaneously sliding one and the other dish elements 8 in the guides formed by the grooves 17. It will be noted to what point the pinion gears 6, the assembly pin 9 and the two dish elements 8 are easily and rapidly mounted, insofar as they are all positioned at the same time. The step being described is terminated once the other axle pinion 5 and the other dish element 7 have also been disposed inside the cage 2, and the obturator 3 has been pre-positioned at the level of the access opening 10.

The step of adjusting the drag torque of the differential or of the play, along axis A, of the mechanism inside the body 1 then begins. This adjustment is effected by screwing the cover 21 more or less deeply in the cage 2, which may be effected by an automat acting from a continuous measurement or from successive measurements of the drag torque. In a variant, it is possible to proceed in the following manner: one begins by screwing the obturator 3 in the cage 2 completely, i.e. until they come into abutment, then this obturator 3 is unscrewed by a quantity corresponding to the desired play. It will be noted that the threaded portions 12 and 24 in cooperation form means for adjusting with precision the relative position, in approach-removal along axis A, of the cage 2 and of the obturator 3. As the assembly pin 9 is mounted to slide along axis A, with the aid of the dish elements 8, it is positioned by itself inside the cage 2, with the result that the axial plays of the two axle pinions 5 are adjusted simultaneously in one operation.

Once the relative position of the cage 2 and of the obturator 3 is adjusted, these latter are immobilized with respect to each other with the aid of locking means which, in the example shown, are formed by a welding bead 31 arranged along the edge of the cover 21, as well as by a pin 32 inserted by force in a hole pierced both in the cage 2 and the obturator 3, where the end portion 11 and the cylindrical surface 22 cooperate.

The adjustment and assembly which have just been described are particularly simple and rapid to carry out, in accordance with the object that the invention intends to attain.

Moreover, contrary to the prior art mentioned in the introduction, it is not necessary to manufacture, manage and store a whole set of dish elements of different thicknesses.

In addition, the adjustment of the play or of the drag torque may be automatized.

FIG. 1 shows the differential as arranged when all the steps for assembly described previously have been carried out. The cage 2 and the obturator 3 are in that case rigidly associated coaxially. They retain therebetween, with reduced play in the direction defined by axis A, the whole mechanism and in particular the axle pinions 5. The pin 9, on which the pinion gears 6 are idly mounted, is therefore common to the latter, this simplifying the assembly of the differential and giving the whole an increased rigidity. The shape of the seats 29 of the dish elements 8 is such that it promotes the rotation of the pinion gears 6, just like the anti-friction dish elements 7 promote the rotation of the axle pinions 5. These anti-friction dish elements 7 are all the more useful as the surfaces of the body 1 on which they are applied are not machined.

The invention is not limited to the form of embodiment described hereinbefore.

In particular, one of the two locking means constituted by the welding bead 31 and the pin 32 may be eliminated, while retaining the other. Moreover, these locking means may be replaced or completed by others, such as for example a threaded ring, clamped against the cover 21 by screwing in the cage 2, in the manner of a counter-nut. The desired locking may also be obtained by crimping the cage 2 on the obturator 3 or by adhesion.

Moreover, although the differential described hereinbefore by way of example comprises only two pinion gears 6, a differential which presents more of them, for example three or four, does not depart from the scope of the invention.

With respect to the known differentials in which no adjustment of the drag torque is effected, a differential according to the invention presents improved operational performances. 

1. Differential body inside which are intended to be mounted two axle pinions (5) and at least two pinion gears (6), each in mesh with the two axle pinions (5), this body comprising first (2) and second (3) parts intended to be assembled, these first (2) and second (3) parts comprising complementary guiding means (11, 22) adapted to guide them in relative approach and removal along the axis of rotation (A) of the differential, characterized in that said first part comprises at least two inner guides (17) for slidably mounting at least one pin (9) for rotatable assembly of at least one of the pinion gears (6), each of these two guides (17) joining two points offset from each other in a direction parallel to the axis of rotation (A) of the differential.
 2. Body according to claim 1, characterized in that the first and the second part comprise means (12; 24) for adjusting their relative position in approach-removal.
 3. Body according to claim 2, characterized in that said adjusting means comprise a threading and a tapping, which are complementary, provided on at least a part (12; 24) of the guiding means (11; 22).
 4. Body according to claim 1, characterized in that said first part presents the shape of a cage (2) essentially defining a housing (4) at least for the axle pinions (5) and pinion gears (6), this cage comprising an opening (10) for access to said housing (4), this opening (10) being intended to be obturated by said second part (3).
 5. Body according to claim 4, characterized in that said first part is a forged piece, at least the essential of its inner surface (15, 16, 17) which defines said housing (4) not comprising a trace of machining.
 6. Differential comprising at least: two axle pinions (5), two pinion gears (6), each in mesh with the two axle pinions (5), and a body (1) inside which are mounted the axle pinions (5) and the pinion gears (6), this body (1) comprising assembled first and second parts (2, 3), characterized in that the body is in accordance with any one of the preceding claims, at least one pin (9) for rotatable assembly of the pinion gears (6) being mounted to slide, the relative position of said first and second parts (2, 3) being adjusted so that the axle pinions have a predetermined axial play or so that the differential has a predetermined drag torque, said first and second parts (2, 3) being locked in this adjusted relative position.
 7. Differential according to claim 6, characterized in that this differential comprises two parts (8) of which each defines a housing receiving an end of said or of one of a plurality of pins (9) for rotatable assembly of the pinion gears (6), each of said guides presenting the shape of a groove (17) in which one of the two parts (8) slides.
 8. Differential according to claim 6, characterized in that it comprises a pin (32) for locking the first and second parts (2, 3) in said adjusted relative position.
 9. Differential according to claim 6, characterized in that each of the first and second parts (2, 3) comprises an inner surface (16, 25), said inner surfaces being arranged opposite and being substantially concave, the differential comprising two anti-friction dish elements (7), each placed between one of these two substantially concave surfaces (16, 25) and a substantially convex surface of one of the axle pinions (5).
 10. Method for assembling the differential according to claim 6, characterized in that it comprises at least the steps in which: a) at least the axle pinions (5) and the pinion gears (6) are disposed between the first and second parts (2, 3); b) the relative position of said first and second parts (2, 3) is adjusted so as to adjust the axial play of at least one of the axle pinions (5) or the drag torque of the differential, and c) the first and second parts (2, 3) are locked in the position determined during step b.
 11. Method for assembly according to claim 10, characterized in that, before step a), said assembly pin (9) or plurality thereof bearing the pinion gears (6), is/are made to slide inside said first part. 